A serial study of heart function during pregnancy, lactation and the dry period in dairy goats using echocardiography

Echocardiography and Doppler measurements were performed to investigate changes in heart dimensions and function during pregnancy, lactation and the non-pregnant, non-lactating (dry) period in dairy goats. Eight Swedish domestic goats (Capra hircus) were studied with two-dimensional (2DE), M-mode and continuous wave Doppler measurements. Cardiac dimensions did not differ between periods. The mean cardiac outputs were 35 and 28% greater during pregnancy and lactation, respectively, vs. the dry period. Arterial blood pressure (measured by telemetry) did not differ between reproductive periods before echocardiographic measurements, but became elevated during the measurements, with the smallest rise during lactation. Heart rate was elevated during pregnancy and increased further during echocardiographic measurements, but was not elevated during the other periods. The cranial location of the heart influenced the selection of examination window and caused some difficulties in positioning the ultrasound transducer. This may have led to underestimation of the velocity trace integral and therefore to underestimation of cardiac output. However, our values were within the range of these obtained with dye- and thermodilution methods. The goats tolerated the investigations well during lactation and the dry period, but showed increased blood pressure and heart rate during pregnancy. Therefore, the non-invasive and safe echocardiographic-Doppler method appears to be a good alternative for studies of heart dimensions and function during lactation and the dry period in the dairy goat.